1. Field of the Invention
The invention relates to devices and systems for communicating over a network. More particularly, the invention relates to a method and apparatus for streaming a multimedia signal to remote viewers connected to a communication network.
2. Description of the Related Art
The constantly increasing processing power available in hardware devices such as personal computers, personal digital assistants, wireless phones and other consumer devices allows highly complex functions to be performed within the device. The hardware devices can perform complex calculations in order to implement functions such as spreadsheets, word processing, database management, data input and data output. Common forms of data output include video and audio output.
Personal computers, personal digital assistants and wireless phones commonly incorporate displays and speakers in order to provide video and audio output. A personal computer incorporates a monitor as the display terminal. The monitor, or display, on most personal computers can be configured independently of the processor to allow varying levels of resolution. The display for personal computers is typically capable of very high resolution, even on laptop-style computers.
In contrast, displays are permanently integrated into personal digital assistants and wireless phones. An electronic device having a dedicated display device formats data for display using dedicated hardware. The processing capabilities of the hardware as well as the display capabilities limit the amount of information displayed and the quality of the display to levels below that typically available from a personal computer. The lower quality is defined as fewer pixels per inch, the inability to display colors or a smaller viewing area.
A personal computer may integrate one of a number of hardware interfaces in order to display video output on a monitor. A modular video card or a set of video interface Integrated Circuits (IC's) is used by the personal computer to generate the digital signals required to generate an image on the monitor. The digital signals used by a computer monitor differ from the analog composite video signal used in a television monitor. However, the personal computer may incorporate dedicated hardware, such as a video capture card, to translate analog composite video signals into the digital signals required to generate an image on the monitor. Thus, the personal computer may display, on the monitor, video images captured using a video camera, or video images output from a video source such as a video tape recorder, digital video disk player, laser disk player, or cable television converter.
The video capture card, or equivalent hardware, also allows the personal computer to save individual video frames provided from a video source. The individual video frames may be saved in any file format recognized as a standard for images. A common graphic image format is the Joint Photographic Experts Group (JPEG) format that is defined in International Organization for Standardization (ISO) standard ISO-10918 titled DIGITAL COMPRESSION AND CODING OF CONTINUOUS-TONE STILL IMAGES. The JPEG standard allows a user the opportunity to specify the quality of the stored image. The highest quality image results in the largest file, and typically, a trade off is made between image quality and file size. The personal computer can display a moving picture from a collection of JPEG encoded images by rapidly displaying the images sequentially, in much the same way that the individual frames of a movie are sequenced to simulate moving pictures.
The volumes of data and image files generated within any individual personal computer provide limited utility unless the files can be distributed. Files can be distributed among hardware devices in electronic form through mechanical means, such as by saving a file onto a portable medium and transferring the file from the portable medium (e.g., floppy disks) to another computer.
Such mechanical file transfers are not particularly efficient and may be limited by the capacity of the transfer medium. A more efficient method of transferring files between computers is by using some type of communication link. The most basic communication link is a hardwired connection between the two computers transferring information. However, information may also be transferred using a network of computers.
A computer may be connected to a local network where a number of processors are linked together using dedicated communication links. File transfer speed on a dedicated network is typically constrained by the speed of the communication hardware. The physical network is typically hardwired and capable of providing a large signal bandwidth.
More widespread remote networks may take advantage of existing infrastructure in order to provide the communication link between networked processors. One common configuration allows remote devices to connect to a network using telephone land lines. The communication link is the factor constraining data transfer speed where low bandwidth communication links such as telephone land lines are used as network connections.
One well known public network that allows a variety of simultaneous communication links is the Internet. As used herein, “Internet” refers to a network or combination of networks spanning any geographical area, such as a local area network, wide area network, regional network, national network, and/or global network. As used herein, “Internet” may refer to hardwire networks, wireless networks, or a combination of hardwire and wireless networks. Hardwire networks may include, for example, fiber optic lines, cable lines, ISDN lines, copper lines, etc. Wireless networks may include, for example, cellular systems, personal communication services (PCS) systems, satellite communication systems, packet radio systems, and mobile broadband systems.
Individual computers may connect to the Internet using communication links having vastly differing information bandwidths. The fastest connections to the network use fiber connections directly to the network “backbone”. Connections to the network having a lower information bandwidth use E1 or T1 telephone line connections to a fiber link. Of course, the cost of the communication link is proportional to the available information bandwidth.
Network connections are not limited to computers. Any hardware device capable of data communication may be connected to a network. Personal digital assistants as well as wireless phones typically incorporate the ability to connect to networks in order to exchange data. Hardware devices often incorporate the hardware or software required to allow the device to communicate over the Internet. Thus, the Internet operates as a network to allow data transfer between computers, network-enabled wireless phones, and personal digital assistants.
One potential use of networks is the transfer of graphic images and audio data from a host to a number of remote viewers. As discussed above, a computer can store a number of captured graphic images and audio data within its memory. These files can then be distributed over the network to any number of viewers. The host can provide a simulation of real-time video by capturing successive video frames from a source, digitizing the video signal, and providing access to the files. A viewer can then download and display the successive files. The viewer can effectively display real-time streaming video where the host continually captures, digitizes, and provides files based on a real-time video source.
The distribution of captured real-time video signals over a network presents several problems. For example, there is no flexibility in the distribution of files to various users. A host captures the video and audio signals and generates files associated with each type of signal. As previously discussed, graphic images are commonly stored as JPEG encoded images. The use of JPEG encoding can compress the size of the graphic image file but, depending on the graphic resolution selected by the host, the image file may still be very large. The network connection at the host is an initial bottleneck to efficient file transfer. If the host sends files to the network using only a phone modem connection to transfer multiple megabyte files, no viewer will be able to display the video and audio signals in a manner resembling real-time streaming video.
The viewer's network connection becomes another data transfer bottleneck even if the host can send files to the network instantaneously. A viewer with a phone modem connection will not be able to transfer high-resolution images at a speed sufficient to support real-time streaming video.
One option is for the host to capture and encode any images in the lowest possible resolution to allow even the slowest connection to view real-time streaming video. However, the effect of capturing low-resolution images to enable the most primitive system's access to the images is to degrade the performance of a majority of viewers. Additionally, the images may need to be saved in such a low resolution that all detail is lost from the images. Degradation of the images, therefore, is not a plausible solution.
Another problem encountered is the inability of all users to support the same graphical image format selected by the host. Most personal computers are able to support the JPEG image format; however, network-enabled wireless phones or personal digital assistants may not be able to interpret the JPEG image format. Additionally, the less sophisticated hardware devices may not incorporate color displays. Access to video images should be provided to these users as well.
Finally, in such video distribution systems, the viewer has no control over the images. The viewer must rely solely on the host to provide a formatted and sized image having the proper view, resolution, and image settings. The viewer cannot adjust the image being displayed, the image resolution, or the image settings such as brightness, contrast and color. Further, the viewer is unable to control such parameters as compression of the transmitted data and the frame rate of video transmission.